1. Field of the Invention
The present invention relates to an electrical heating device, particularly to an electrical heating device for a motor vehicle. In particular, the present invention relates to electrical heating devices such as those known, for example, from EP 1 253 808 A1 or EP 0 901 311 A1.
2. Description of the Related Art
In these previously known electrical heating devices, a layer structure is located in a frame that forms, on oppositely situated sides, openings for the passage of a medium to be heated. This layer structure comprises layers of corrugated-rib elements and heat generating elements, whereby the heat generating element has at least one PTC element. This PTC element is located between parallel extending contact plates and is fed current via these contact plates. The electrical heating device furthermore has a connecting housing in which at least one power switch that generates power dissipation is provided and to which is assigned a heat sink that lies exposed on the outside of the connecting housing.
The connecting housing is thereby regularly used for the connection of selected, or occasionally all, contact plates to a power switch. This power switch normally comprises a circuit board that normally is provided at least with one semiconductor power switch. This controls the heating power of one or more heat generating elements and thereby generates power dissipation, which must be conducted away. This removal of the power dissipation, i.e., the cooling of the heat sink, normally takes place through the medium that is to be heated in the electrical heating device. This medium is normally air.
The electrical heating device according to the invention can, however, also be used for heating a medium other than air. Consequently it is conceivable to heat a liquid medium, for example, water, with the electrical heating device. The air to be heated can also, depending on the operation of the HVAC into which the electrical heating device is built, have to heat air that carries water with it. Consequently it is conceivable that, in the case of high atmospheric moisture levels and due to the action of the condenser in the HVAC, water precipitates which is carried along with the air. It is also possible for contamination to be carried along.
The control components and current-carrying parts accommodated in the connecting housing should, however, be protected from contamination and moisture that have entered.
On the other hand, an extensive passage opening is created for the heat sink by means of a housing shell that surrounds the connecting housing, whereby this is particularly susceptible to the entry of moisture and contamination.